A hybrid vehicle driveline may include an engine that is directly injected with fuel and a driveline disconnect clutch. The driveline disconnect clutch may be selectively opened and closed in response to vehicle operating conditions. For example, the driveline disconnect clutch may be opened when battery state of charge (SOC) is high and driver demand torque (e.g., torque requested by a driver) is low. The same driveline disconnect clutch may be closed when driver demand torque is greater than a threshold torque or when battery SOC is less than a threshold SOC. The driveline disconnect clutch may also be closed to start the engine via an electric machine in the driveline. However, it may take more time than is desired to get the engine started since the engine is directly injected with fuel.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of engine starting, comprising: rotating an engine in response to a vehicle activation request and in the absence of an engine start request; not supplying fuel to the rotating engine; stopping the rotating engine; and starting the stopped engine in response to an engine start request.
By rotating an engine to increase fuel pressure of a direct injection fuel rail before an engine start request, it may be possible to provide the technical result of starting the engine in less time since fuel pressure may already be at a level that supports fuel injection into engine cylinders. For example, an engine may be rotated without supplying spark and fuel to the engine so that a direct injection fuel pump within the engine increases pressure within a direct injection fuel rail. If a request to start the engine occurs a short time after a desired pressure in the direct injection fuel rail is established, fuel may be injected without having to rotate the engine to reestablish the desired fuel pressure. Thus, it may be possible to rotate the engine less during engine starting, thereby reducing engine starting time.
The present description may provide several advantages. In particular, the approach may reduce engine starting time. Further, the approach may improve vehicle drivability and engine emissions. Further still, the approach may improve driver satisfaction regarding the vehicle driving experience.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.